Geologic map of the Bach region of Mercury

The Bach region encompasses the south polar part of Mercury poleward of lat 65 degrees S. About half of the region was beyond the terminator during the three Mariner 10 encounters and hence not visible. The entire mapped area was covered by near-vertical photography from the second encounter, and the eastern part, from long 15 degrees to about 110 degrees, was covered by oblique photography from the first encounter.